Using Shapekeys in Unity after exporting FBX from Blender
I tried my plan B and simply imported the .blend file instead of the .fbx file since I assumed the exporter was modifying each shapekey. My hypothesis may be correct since the error is subtle to a point of negligibility (unless I activate more than 5 shapekeys at once). I consider this a solution: simply import the .blend instead of exporting a .fbx and re-importing it to unity.